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 Forum index » DIY Hardware and Software » Video synthesis and manipulation
a cmos video Synth
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inlifeindeath



Joined: Apr 02, 2010
Posts: 315
Location: Albuquerque, NM

PostPosted: Thu May 31, 2012 10:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Psyingo wrote:
is this pong schematic you got ntsc or pal?
you should look up the timing signals for h and v sync of ntsc and pal. H and V sync need to be rather stable or you will get scrolling. also unless you get a color encoder chip or manage to make your own color encoder you will only get a b/w signal.

take a look at this, it has some important frequency information. http://www.epanorama.net/documents/video/video_timing.html

i dont think you will get much if you just feed whatever signals into the h and v sync. you need proper timing signals to get a good image. you might get some warbly lines, but it will get boring fast when you can't generate proper shapes and patterns.


ok so wikipedia is telling me that:
Horizontal Frequency 15.734 kHz
Vertical Frequency 60 Hz

So I can figure out how to build stable oscillators at those frequencies, but is it worthwhile to have theses oscillators variable?
And once I have the sync osc's fed in, what kind of input is it expecting or can be fed to the video in?

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Psyingo



Joined: Jun 11, 2009
Posts: 247
Location: Canada

PostPosted: Fri Jun 01, 2012 5:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

inlifeindeath wrote:
Psyingo wrote:
is this pong schematic you got ntsc or pal?
you should look up the timing signals for h and v sync of ntsc and pal. H and V sync need to be rather stable or you will get scrolling. also unless you get a color encoder chip or manage to make your own color encoder you will only get a b/w signal.

take a look at this, it has some important frequency information. http://www.epanorama.net/documents/video/video_timing.html

i dont think you will get much if you just feed whatever signals into the h and v sync. you need proper timing signals to get a good image. you might get some warbly lines, but it will get boring fast when you can't generate proper shapes and patterns.


ok so wikipedia is telling me that:
Horizontal Frequency 15.734 kHz
Vertical Frequency 60 Hz

So I can figure out how to build stable oscillators at those frequencies, but is it worthwhile to have theses oscillators variable?
And once I have the sync osc's fed in, what kind of input is it expecting or can be fed to the video in?


The oscillator should be variable over a small range to adjust proper sync but it shouldn't be variable in the vco sense. Sync needs to stay locked at a constant frequency to work well.

there are blanking periods in video that need to be adhered to as well as voltage levels. i think composite is around a couple volts peak to peak, i wouldn't advise going much over that.

Once you get blanking done you can input any signal but very fast signals will produce better visuals. in the supersonic region. Anything under the h sync will produce a horizontal bar or flicker of some kind.
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inlifeindeath



Joined: Apr 02, 2010
Posts: 315
Location: Albuquerque, NM

PostPosted: Sat Jun 02, 2012 8:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

my bad. it wasnt a pong schem, it was from a System 80 (http://www.classic-computers.org.nz/blog/2010-08-27-s80-wavy-screen-fix.htm

More specifically, what i've built is the Sync Gen and Video Mixer from this schematic http://www.classic-computers.org.nz/system-80/manuals_tm3_drawing%204.6_cassette%20interface%20Mk%201%20schematics.jpg
The crystal clock (upper left hand corner) in this 2nd schem is the oscillator i posted and i added a divider. Also, schematic points "A, B, and V" from the sync gen, connect on this second schem http://www.classic-computers.org.nz/system-80/manuals_tm3_drawing%204.5_video%20interface%20card%20schematics_blue%20label%20series.jpg
Hope this makes sense.

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inlifeindeath



Joined: Apr 02, 2010
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Location: Albuquerque, NM

PostPosted: Sat Jun 02, 2012 8:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

also, i dont really understand the blanking period. I get that it's the reset point for v and h lines (right?) but not how it's implemented and/or applied?
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RingMad



Joined: Jan 15, 2011
Posts: 233
Location: Montreal, Canada
Audio files: 2

PostPosted: Sun Jun 03, 2012 5:52 am    Post subject: Reply with quote  Mark this post and the followings unread

EDIT: I moved the schematic and description of my CMP-DIV Video Effecter AKA Vidiffektor to its own thread here:

http://electro-music.com/forum/topic-54113.html

James

Last edited by RingMad on Fri Jun 22, 2012 3:42 am; edited 1 time in total
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inlifeindeath



Joined: Apr 02, 2010
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Location: Albuquerque, NM

PostPosted: Mon Jun 04, 2012 1:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

very cool ringmad! thanks for posting, i'll have to give it a try!

Psyingo, you still there? Sorry for all the questions, i appreciate your help!

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Psyingo



Joined: Jun 11, 2009
Posts: 247
Location: Canada

PostPosted: Mon Jun 04, 2012 2:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sorry, i was away all weekend for a festival i was performing at. I got to debut the video Synth in front of an audience. That was nice.

Blanking is a period where the video signal is not present at the beginning and end of a frame and line. You could blank a signal a number of ways, using village controlled switches or logic gates for example. You switch the video signal off for the specified blanking period to allow the display monitor time to fly back.
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Psyingo



Joined: Jun 11, 2009
Posts: 247
Location: Canada

PostPosted: Thu Jun 07, 2012 9:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

RingMad wrote:
OK, sorry... finally... as promised earlier in this thread, my schematic for the CMP-DIV Video Effecter AKA Vidiffektor, even though it's a bit off-topic, and is only half CMOS. And produces results nowhere near as cool as Psyingo's work.

My friend who actually came up with the circuit had originally conceived it for audio, but then we wondered what it might do with video. We each took it in slightly different directions, but the core idea remains.

Warning: Use at your own risk. I cannot guarantee that this won't break equipment this is connected to. In certain cases, this can add a DC offset to the output signal, so it ends up between 1V and 2V. It is beyond my electronics knowledge to know if this is bad or not.

James.

EDIT: P.S. I used this circuit to produce my avatar-self-portrait... those wavy lines.


Ringmad, maybe you can post this separately in the new video Synth forum, where this thread now resides. That way people can find it easier.
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Psyingo



Joined: Jun 11, 2009
Posts: 247
Location: Canada

PostPosted: Thu Jun 07, 2012 9:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here is a pic of the unfinished front panel! Still more work to be done inside and out.

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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brock



Joined: May 26, 2011
Posts: 96
Location: Canada

PostPosted: Thu Jun 21, 2012 10:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

Nice work there Psyingo. I find this quite inspiring and hope to contribute when I can.

I read through the other video synthesis threads and noticed that Lars, aka creatorlars, actually finished his design with Ed Leckie and is selling modules through analoguehaven. Here's a few links to his stuff. Looks good, worth aspiring to.

http://www.lzxindustries.net/
http://www.analoguehaven.com/lzxindustries/
http://www.youtube.com/user/lzxindustries?feature=watch

I look forward to seeing how this progresses.
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Psyingo



Joined: Jun 11, 2009
Posts: 247
Location: Canada

PostPosted: Mon Jul 09, 2012 6:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

here is a video clip of some vjing i did the other night. i provided visuals to a bunch of artists/djs...

it turned out alright.

the camera kind of craps out trying to capture it though. so it seems a lot more flickery than it really is.

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brock



Joined: May 26, 2011
Posts: 96
Location: Canada

PostPosted: Sun Aug 19, 2012 10:59 am    Post subject: Reply with quote  Mark this post and the followings unread

It's tough to capture video without a genlock camera, probably tougher trying to record vga. Interesting stuff you're doing though.
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jean bender



Joined: Feb 21, 2010
Posts: 133
Location: france

PostPosted: Sat Nov 02, 2013 10:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi !! I'm coming back there..
I'm wondering if any of you would have some links or documentation about the way sync works.. I still can't really get it. Should the sync always melt with other datas ?

How different interfaces are syncing each other ? Do they all have the same sync kind ?

And, at least, reffering to Inlifeindeath post, most of the components used on the first schematic are "normal" logic gates ? But for the clock on the second schematic, is it important to use the whole components, or should it be possible to eliminate some of them ?

thanks for any answers !

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brock



Joined: May 26, 2011
Posts: 96
Location: Canada

PostPosted: Tue Nov 05, 2013 11:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi jean,

Here is a link to a file http://www.eng.ucy.ac.cy/theocharides/Courses/ECE664/VGA.pdf that does a good job of explaining video sync. It also describes blanking signals which you will find just as important as sync.

More info on VGA timing, http://www.epanorama.net/documents/pc/vga_timing.html.

For video synthesis you usually want to sync all of your pattern and image generation circuits to the video timing signals, either sync or blanking. So these signals will reset or trigger whatever you want to display.

I'm not sure what you mean by different interfaces syncing each other.

I'll post a simple VGA sync and blanking signal generator schematic in a few days.

Brock
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jean bender



Joined: Feb 21, 2010
Posts: 133
Location: france

PostPosted: Wed Nov 06, 2013 2:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Brock !!

Happy to see that somebody is still there !! Thanks for the informations you share, that's appreciated !

By different gear syncing each other, my question is more to know if there's an unique sync that will work for a whole system, or if different modules need different sync, and so on, how i should melt them !

thanks again !

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jean bender



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PostPosted: Wed Nov 06, 2013 2:44 am    Post subject: Reply with quote  Mark this post and the followings unread

and last but not least :

Is it better to work on VGA, or Composite ? Most of television use composite.. Is it the same thing, or really different ?? Sorry for these noob questions..

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brock



Joined: May 26, 2011
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PostPosted: Wed Nov 06, 2013 7:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

jean,

There is no master sync for video. Timing is different for all systems and formats, even syncing between the same formats is tricky as the signals have to match up perfectly - they make genlocks and time base correctors and other stuff for that.

I think 'melt' is not the right word. Melt en francais est fondre, maybe you are thinking meld? I think you are asking, how does everything hook up together? and that's a hard question to answer as it is difficult at best, and also depends on what you are trying to do. You can probably count on having a special circuit for every type of signal you want to connect to your video synth. The way it works is that everything syncs to the video timing signals and all analog signals will be level shifted, attenuated or amplified to meet the 1V or less output signal requirements.

The VGA or composite video question is also tough to answer.

First the differences: VGA has a bunch of separate signals, 2 sync, horizontal and vertical, plus 3 analog video signals for red, green and blue. You also need 2 blanking signals, horizontal and vertical, to control the analog signals.

Composite combines all the required signals into one - hence composite - so horizontal and vertical sync, plus chrominance and luminance, and the chroma carrier (color burst) are all mixed into one.

A VGA synth is probably easier to build as you don't need anything special so you can use cheap parts, and it's easier to understand what is going on with progressive scanning. The down side of VGA is it's usually hard to record, unless you have a video card that accepts RGB in.

There are lots of ways to build a composite video synth. You can do it the same way as a VGA one, with sync and RGB signals but instead of directly driving a monitor it drives a RGB encoder ship - there are still a few of them around although with most video going digital, composite encoders and decoders are going out of production really quickly.

You can also build up a composite signal from scratch using cmos switches to combine the various parts. The timing is more complicated than VGA and you need a few more signals and the chroma carrier, and you probably want a chroma modulator too. I don't know of any DIY schematics for this, but it's all possible with inexpensive parts.

Maybe the easiest way to get started is with a video source such as a dvd player or a camera that has composite out, extract the timing signals with a couple of comparators and modify or replace the original source.

Not sure if this is any help as there are so many possibilities. Maybe it's easier to think of this way, if you want to modify or work with existing video, it's probably easier to start with composite; if you want to create stuff from scratch, start with VGA.
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jean bender



Joined: Feb 21, 2010
Posts: 133
Location: france

PostPosted: Mon Nov 18, 2013 1:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Brock !! thanks for your answers ! I'm a bit busy due to my work, but i gonna check all that.. and i'll give some news from my work here !
cheers !

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